Directional fastener assembly

ABSTRACT

A directional backing plate and threaded nut for securing the traction device relative to a flexible rotatable track. The backing plate and nut define noncircular curvilinear peripheries defined by a major axis and a minor axis, wherein the major axis is greater than the minor axis. The backing plate and threaded nut cooperatively engage the stud relative to the track, such that the major axis is substantially perpendicular to the direction of rotation of the track, and the minor axis is substantially parallel to the direction of rotation.

This is a continuation of U.S. Ser. No. 07/723,331, filed Jun. 28, 1991now U.S. Pat. No. 5,188,441.

The present invention relates to fasteners, and more particularly to adirectional fastener assembly for affixing a traction stud to a flexiblerotatable track.

BACKGROUND OF THE INVENTION

Vehicles driven over adverse riding surfaces, such as snow, ice, or mudemploy traction devices to improve operating performances. The tractiondevices include a substantially cylindrical stud having either a conicalor wedge shaped bit. The conical bit defines a circular cone having acircular cross section transverse to the direction of penetration intothe riding surface. The tip of the cone penetrates the riding surface toimprove traction. The wedge shaped bit defines a planar wedge whichpenetrates the riding surface to improve traction.

The bit is either affixed to the stud or integrally formed with thestud. The stud includes a threaded portion and a peripheral flangedefining wrench flats.

A washer and T-nut are used to affix the stud to the track. The washershave either a circular or a square periphery. The washer includes aconcentric aperture sized to receive the cylindrical portion of thestud. The portion of the washer adjacent the aperture is convex forminga domed portion defined by a spherical radius of approximately 2 to 3inches. The T-nut is a planar circular piece having a threaded sleeveprojecting from one side. Three prongs extend from the same side. Theprongs are equally spaced approximately 120° apart about the periphery.The stud is passed through the washer so that the wrench flats contactthe convex side of the washer. The threaded portion of the stud is thendisposed through an aperture in the track so that the threaded portionextends towards the inside of the track. The T-nut engages the stud anddraws the wrench flats against the washer, thereby drawing the washeragainst the track, and the prongs of the T-nut into the back side of thetrack.

Due to the tremendous forces exerted upon the traction device, it isdesirable to have the contact area between the washer, T-nut, and thetrack as large as possible. The large surface area minimizes damage tothe track as forces are exerted on the traction device. However, thelarge contact surface area has specific drawbacks. The edges of thelarge surface area introduce excessive wear as the track passes over theidler wheels. The flexing of the track over the idler wheels causes theedges of the washer and T-nut gouge the track. Therefore, there arebenefits to reducing the contact area. In addition, as the T-nut rotatespast the idler wheels, the prongs-temporarily disengage the track, andthen re-engage as the T-nut passes beyond the idler wheel. The repeatedwithdrawal and insertion of the prongs into the track locally weakensthe track.

In an attempt to provide a balance between increased contact area andtrack wear, transverse cleats have been used across the width of thetrack. The cleats extend perpendicular to the direction of rotation. Aplurality of traction devices may be cooperatively engaged with thetrack along the width of the track. However, the cleats require aplurality of traction devices, and add significant weight to the trackwhich weight also introduces extra wear.

SUMMARY OF THE INVENTION

The present invention includes a directional fastener assembly having adirectional backing plate and directional T-nut for providing increasedcontact area between the traction device and the track, while minimizingthe resistance to rotation and track degradation.

Preferably, the backing plate has an obround configuration and includesa concave surface having a larger radius of curvature than the washersof prior art. The obround configuration is defined by a major axis and aminor perpendicular axis, wherein the major axis is longer than theminor axis.

The backing plate cooperates with the directional T-nut to retain thetraction device relative to the track. The T-nut is defined by anon-circular curvilinear periphery, having a major axis and aperpendicular minor axis such that the major axis is greater than theminor axis. The directional backing plate and T-nut cooperate to affix astud relative to the track, such that the major axis of the T-nut andbacking plate are substantially perpendicular to the direction ofrotation of the track, and the minor axes are substantially parallel tothe direction of rotation.

The fastener assembly provides a reduced length of contact with thetrack in the direction of rotation, thereby reducing the amount ofcutting into the track by the edges of the backing plate and the T-nut.The fastener assembly also provides an increased contact areaperpendicular to the direction of rotation, thereby distributing forcesover a larger area to reduce wear on the track.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial side elevational view of the fastener assembly in anoperating environment;

FIG. 2 is a bottom plan view of the directional T-nut showing theobround periphery;

FIG. 3 is a cross-sectional view taken along lines 3--3 of FIG. 2;

FIG. 4 is a top plan view of the directional backing plate;

FIG. 5 is a cross-sectional view taken along lines 4--4 of FIG. 5;

FIG. 6 is an exploded partial cross-sectional view of the directionalfastener assembly relative to a flexible track; and

FIG. 7 is a partial cross-sectional view of a directional fastenerassembly cooperatively engaging a traction device and a flexible track;

FIG. 8 is a top plan view of a directional fastener assembly forsecuring a threaded stud to a rotatable flexible track showing theorientation of the major axis and the minor axis of the directionalt-nut relative to the direction of the track rotation; and

FIG. 9 is a bottom plan view of a directional fastener assembly forsecuring a threaded stud to a rotatable flexible track showing the majoraxis and the minor of the directional backing plate relative to thedirection of track rotation.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to FIG. 1, the directional fastener assembly 10 of the presentinvention retains a traction stud 12 relative to a rotatably flexibletrack 16. As shown in FIGS. 6 and 7, the traction stud includes athreaded portion 13 and peripheral wrench flats 15. The fastenerassembly 10 includes a directional backing plate 40 and directionalT-nut 60.

Referring to FIGS. 4 and 5, the backing plate 40 is defined by acurvilinear noncircular periphery 42. The periphery 42 may besubstantially oval, and is defined by a major axis MAJ and aperpendicular minor axis MIN, wherein the major axis is longer than theminor axis. The backing plate 40 defines an obround periphery 42, thatis, having the form of a flattened cylinder having parallel sides 46 andsemicircular ends 48. Preferably, the parallel sides 46 extend parallelto the major axis MAJ for a length of 1/16" to 1/4" with a preferredlength of approximately 1/8". The parallel sides 46 are connected by thesemicircular curved ends 48 having by a radius of approximately 3/8" to5/8" with a preferred radius of approximately 1/2".

Each of the sides 46 are of equal length, and each of the curved-ends 48are of equal length, such that the sides are interconnected by thecurved semicircular ends. Preferably, the parallel sides 46 defineapproximately 2/25 the periphery of the backing plate 40, wherein theratio of minor axis min to major axis MAJ is from approximately 4:5 to19:20 with a preferred ratio of approximately 8:9. That is, the minoraxis has a length from approximately 80% to approximately 95% of themajor axis. The backing plate 40 includes a central aperture 43 having adiameter sufficient to receive the specific traction device employedwith the fastener assembly. The diameter of the central aperture 43 maybe from approximately 1/4" to 5/16" with a preferred diameter of 17/64".

The backing plate 40 includes a circumscribing rib 44 set back from theperiphery by approximately 0.06". The rib 44 defines a convex surfacehaving a cross section transverse to the longitudinal dimension ofapproximately 0.12".

The backing plate 40 defines a concave surface 49 within the area of therib 44, wherein the surface 49 is defined by a radius of curvature ofapproximately 4 to 10 inches. The concavity functions to bias thethreads of the stud 12 against the threads of the T-nut 60 whencooperatively engaged with the track 16. The increased radius ofcurvature reduces the amount of dome, or concavity, thereby increasingthe effective contact area between the backing plate 40 and the track 16for the given periphery of the backing plate. The increased effectivecontact area distributes the clamping pressure over a larger area tominimize damage to the track 16. Preferably, the backing plate 40 isformed of heat treated 1070 spring steel.

Referring to FIGS. 2, 3, 6 and 7, the directional T-nut 60 includes asubstantially planar member 61 defined by a noncircular curvilinearperiphery 62. The periphery 62 may be substantially oval andspecifically obround, defined by a major axis MAJ and a perpendicularminor axis MIN, wherein the major axis is greater than the minor axis.Preferably, the periphery 62 of the T-nut 60 satisfies the same ratio ofminor axis MIN to major axis MAJ, as the backing plate 40, and theperiphery 62 of the T-nut 60 is substantially coincident with theperiphery 42 of the backing plate 40. That is, the periphery 62 of theT-nut 60 exhibits the same dimensions as the periphery 42 of the backingplate 40. However, the periphery of the T-nut may be less than orgreater than the periphery of the backing plate, while having the sameaxes ratios.

The T-nut 60 includes a central aperture 63 sized to receive thecylindrical portion of the stud 12. The T-nut 60 includes a threadedsleeve 64 extending from the planar surface 61, concentric with thecentral aperture 63. The threaded sleeve 64 cooperatively engages thethreaded portion of the stud 12. The outer diameter of the sleeve 64 issized to be disposed within an aperture in the track.

A pair of depending prongs 72 extend from the planar surface 61 of theT-nut 60 in the same direction as the sleeve 64. The prongs 72 engagethe track 16 to prevent rotation of the T-nut 60 relative to the track.Preferably, the prongs 72 are located at opposite ends of the major axisMAJ. As the prongs 72 will be colinearly aligned perpendicular to theaxis of rotation, the prongs are not forced to withdraw and reinsertinto the track 16 each time the assembly passes the idler wheel.

Alternatively, the periphery of the backing plate to and T-nut 60 maycomprise a plurality of linear segments (not shown) which define anoncircular substantially oval periphery wherein the dimensionperpendicular to the direction of rotation is larger than the dimensionparallel to the direction of rotation.

To employ the fastener assembly 10, an aperture 17 is formed in thetrack 16 in the desired location of the traction stud 12. The stud 12 isthen disposed through the backing plate 40, such that the convex surfacecorresponding to the concave surface 49 of the backing plate contactsthe peripheral flange formed by the wrench flats 15 on the stud. Thebacking plate 40 and stud 12 are then disposed relative to the track 16,such that the threaded portion 13 of the stud extends into the aperture17. The concave surface 49 contacts the track 16.

The backing plate 40 is aligned so that the major axis MAJ issubstantially perpendicular to the direction of rotation of the track 16and the minor axis MIN is substantially parallel to the direction ofrotation. That is, the parallel sides 46 of the backing plate 40 areperpendicular to the direction of rotation of the track.

The threaded sleeve 64 of the T-nut 60 engages the threaded portion 13of the stud 12. The T-nut 60 is pressed into the track 16 so that theprongs 72 engage the track, and the major axis MAJ is perpendicular tothe direction of rotation and the minor axis MIN is parallel to thedirection of rotation. The stud 12 is threaded into the T-nut 60, untilthe backing plate 40 and the T-nut 60 are substantially coplanar withthe respective surfaces of the track.

The dimension of the contact area perpendicular to the direction ofrotation distributes the clamping force over a relatively large area,and the lesser dimension of the area of contact parallel to thedirection of rotation reduces wear induced by flexing or rotation of thetrack 16.

Preferably, the dimension of the contact area parallel to the axis ofrotation corresponds to the diameter of the idler wheel so that uponrotation of the directional fastener assembly over the idler or drivewheel, the ends of the contact area parallel to the direction ofrotation do not degrade the track. The dimension of contact between thefastener assembly and the track 16 perpendicular to the direction ofrotation is greater than dimension of contact parallel to the directionof rotation.

While a preferred embodiment of the invention has been shown anddescribed with particularity, it will be appreciated that variouschanges and modifications may suggest themselves to one having ordinaryskill in the art upon being apprised of the present invention. It isintended to encompass all such changes and modifications as fall withinthe scope and spirit of the appended claims.

What is claimed is:
 1. A traction assembly for a continuous flexiblerotating track, the track having an inner surface, and an outer surfacefor contacting a support surface, the traction assembly comprising:(a) ashaft having a first end and a second end; (b) a substantiallynoncircular first plate at the first end of the sheet, the first platehaving a surface for contacting the inner surface of the track, thesurface defined by a first dimension and a second longer dimensionperpendicular to the first dimension; and (c) a securing platecontacting the shaft, the securing plate and the first plate adapted tocontact a portion of the track therebetween, wherein the first plate isaligned with the direction of track rotation such that the second longerdimension is perpendicular to the direction of track rotation forreducing stress on the inner surface of the track as the track rotates.2. The traction assembly of claim 1, wherein the first plate isreleasably attached to the shaft.
 3. The traction assembly of claim 1,further comprising retaining means for retaining the securing platerelative to the shaft, wherein the retaining means includes threads on aportion of the shaft and a threaded member for engaging the threadedportion of the shaft to dispose the securing plate intermediate of thethreaded member and the first plate.
 4. The traction assembly of claim1, wherein the securing plate has a substantially curvilinear periphery.5. The traction assembly of claim 1, further comprising protuberancesprojecting from the first plate for engaging the inner surface of thetrack to substantially preclude rotation of the first plate uponoperable engagement with the track, the protuberances extending from thefirst plate along the second longer dimension of the first plate.
 6. Thetraction assembly of claim 5, wherein the protuberances includedepending prongs substantially colinear with the second longerdimension.
 7. A traction assembly for a continuous flexible rotatingtrack, the track having an inner surface, and an outer surface forcontacting a support surface, the traction assembly comprising:(a) atraction stud; (b) an inner plate connected to the stud for contactingthe inner surface of the track, the inner plate having a minor axis anda longer major axis perpendicular to the minor axis, the major axisbeing substantially perpendicular to the direction of rotation of thetrack; and (c) securing means connected to the stud for contacting theouter surface of the track to retained a portion of the track betweenthe inner plate and the securing means.
 8. The traction assembly ofclaim 7, further comprising depending protuberances on the inner platealigned along the major axis for engaging the inner surface of the trackto substantially preclude rotation of the inner plate relative to thetrack.
 9. The traction assembly of claim 7, wherein the securing meansincludes a securing plate connected to the stud and contacting the outersurface of the track, the securing plate having a minor axis and alonger major axis perpendicular to the minor axis, the major axis beingsubstantially perpendicular to the direction of rotation of the track.10. A method of affixing a traction assembly having a stud to acontinuous flexible rotating track, the track having an inner surfaceand an outer surface for contacting a support surface, the methodcomprising:(a) passing a portion of the assembly through the track; (b)connecting an inner plate to the stud, such that the inner platecontacts the inner surface of the track, the inner plate having a minoraxis and a longer major axis perpendicular to the minor axis; (c)aligning the inner plate such that the major axis is substantiallyperpendicular to the axis of rotation of the track; and (d) connecting asecuring plate to the stud such that the securing plate contacts theouter surface of the track to retain a portion of the track between theinner plate and the securing plate.